Method and means for foundry practice



Patented June 20, 1933- CHARLES MARSHALL SAEGER, JR, BOWMANSTOWN,PENNSYLVANIA METHOD AND MEANS FOR FOUNDRY PRACTICE No Drawing. I

Application filed February 17, 1930. S'erial 1%.,429222.

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sive, laborious and dusty task frequently requiring the use of pneumaticohisels and other tools, while in the machining of such castings theintegral film of sand and metal is diflicult to machine unless the toolin its first cut penetrates'beyond the depth of such 5o film. f

In. the prior art many cracked castings have been produced due to hardcores and molds which do not crush readily as the metal casting cools,contracts and solidifies, and such castings are a constant source ofsubstantial loss in all foundries but more especially in aluminum andkindred metal castings.

A further constant source of substantial loss in the prior art of metalcasting has resulted from mold and core blows due to the lowpermeability of the sand forming such molds and cores. Y In the pastmany endeavors have been made to-overcom these very objectionableconditions and losses. Some of these attempts have been to form themolds and cores of green sand, which-is the ordinary molding sand ofcommerce, but the liability of such molds and cores to-bewashed in partinto the molten flowing metal being cast prevents, or renders hazardous,their use in many cases.

To provide molds and cores of more strength than possessed by green sandmolds and, cores, it heretofore has been common practice to embody'abinder in the sand of, eithr or all, clay, molasses and water, flour and,water, and oil, and to indurate such molds and cores by baking. Suchmolds and cores have all' the aforesaid defects except the tendency towash into the flowing molten metal, while the thus formed harder moldsand cores increase the cracking liability ofthe castings as well as tendto increase the metal wascast therein or thereabout; but

such a practice adds a very substantial fire hazard and explosionhazard. Furthermore,

such volatiles become impregnated in the air, breathed by theoperatives, which tend to harmfully aflect the operatives physically andin their efliciency. r

My present inventionf'relates to an improved method and means 'forfoundry practice. Its object is to overcome the aforesaid conditions, tocheaply and readily produce a mold or core of as great, and evengreater, strength, durability and permeability than normal strength, toproduce a mold or core which may be used advantageously at very laterperiods of time than is possible with molds or cores "of the prior art.To attain theseand other objects, and in accordance with'the 'generalfeatures of this unitary invention ofrelated and interdependentcomponents, gniy improved method contemplates the employment of latex.,Thfs substance is the natural rubber substantially as it comes from theplant, usually with the addition of a preservative, and which normallycontains a substantial water content. In some rubber growing regions theWater content of the latex is reduced substantially by evaporation, inthe. presence of a protec- Y tive colloid, in order 'to avoid thesubstantial shipping cost of the water content.

The latex may be mixed directly With the dry sand which is to be madeinto a mold or core, but such mixing is an extremely diflicult operationto bring it into an intimate mixture due, among other conditions, to,what may be properly termed as the thirstiness of the sand whichsubstantially segregated the latex solids and requires their beingmechanicall divided and intimately commingled in the sand in the mixingprocess. In the more advantageous and economic practice of my method, Iprefer to moisten the sand more nearly to the moisture content requiredfor proper molding consistency and then mixing the latex. into such freemoistened sand. This enables the more ready attainment of an intimatemixture of the latex and the sand. 4

A still more eflicient intimate mixture of the sand and the latex may beattained more readily and inexpensively by adding to-the water withwhich the dry sand is mixed a suitable protective colloid such asgelatin, agar agar, glue, sodium and ammonia soaps, extract of quinceseed, or the like, water soluble substances. Such substances added tosuch water reduces the surface tension of the sands and lubricates thesurface of the sand grains, as well as the surface of the solidparticles in the latex and at the same time saturating with water thesand and any clay content without tending to solidify the solidscontained in the latex, thereby avoiding aggregation and facilitatingthe intimate mixture of the solids of the latex throughout the sandgrains of the mold. This enables the molding sand to be tempered to theproper consistency with a substantially less water content. It isoptional with those desiring to practice my method in the manner laststated by mixing with the latex any one or more of the aforesaid orother suitable protective colloids and water to the extent required togive the sand its proper molding consistency; or the water instead ofbeing added to the latex and colloid mixture may be, if desired, firstmixed with the sand.

With the natural water content of the latex, I have found it unnecessaryto add water, either to the sand,'or to the latex, and colloid mixture,but in cases where the latex is partially dehydrated, a suitableaddition of water content may be added either to the sand or to thelatex colloid mixture to give the molding sand its proper moldingconsistency.

Preferably, the next step of my method contemplates the making of therequisite molds and/or cores.

It is further contemplated that 'the latex mixture above stated may beemployed with or without the addition of any of the wellknownvulcanizing' ingredients. When such vulcanizing ingredients are added,they may be either of the atmospheric or the artificial air curing orheat curing variety. lVhere the air curing variety may be ap )lied. themold or core is subjected to atmosp ieric conditions for a suflicientperiod to vulcanize the sand, and where the heat curing vulcanizingagent is employed, the mold or core is subjected to the requisiteelevated temperature to cure the same to the degree of strength requiredby each particular mold or core or class thereof.

During such vulcanizing period, or during the period between themakingand the using of the unvulcanized molds or cores, the surfacesthereof have their moisture contents reduced by evaporation.

The mold or core thus produced is then used in "the making of a casting,most usually by having the molten metal poured thereon or thereabout.Where molten metal is poured into or about the mold or core, its heatcoming in contact with the surfaces of the molds and/or cores causes agas to be formed which permeates the cavity in the mold to be occupiedby the molten metal. This gas is in direct contact with the surfaces ofthe metal in the mold and through which gas the metal is being poured oris otherwise maintained in intimate contact with said gas. As the metalis poured into the molds this gas attains a pressure in the moldcavitybut such pressure is higher between the molten-metal and thesurface or surfaces of the mold covered thereby. This gas pressurecauses the mold or core to become more or less permeated by said gas.This permeation tends to filter or condense, either or both, from thegas the constituents thereof and to deposit the same upon the walls ofthe mold or core. This gas and/or said filtration or condensationproduct prevent the sand or other eai'thy constituents of the mold'orcore from becoming embedded into or adhering to the surfaces of thecasting when made with a mold or core in the practice of my method.

This result is also contributed to by the fact that the heat of themolten metal applied to the surfaces of the mold and/or core tends todecompose some or all of the said materials added to the sand and orother earthy content of the mold or core. This decomposition in whole orin part tends to form a protective,

.insulating or other coating or medium intermediate the juxtaposedsurfaces of the molten metal and the mold and/or core whichsubstantially tends or contributes to the prevention of the normaltendency of the earthy particles of the mold and/or core from beingembedded into or adhering to the surfaces of the casting.

My method also substantially reduces or practically eliminates thetendency toward nxidization of the surfaces of the cast metal.

My method further substantially decreases the normal tendency of themetal surfaces of the casting in contact with the mold, particularlyiron castings and the like, from peeling or hardening and thus makingthin castings more brittle and all castings surfaces more difficult tomachine than heretofore.

The aforesaid steps may also be said to be included in, or to comprisethe method of,

slowing up the cooling rate of the castings made in or about such moldor cores and which substantially contributes to the avoid ance of saidbrittleness of thin iron castings and the machining difliculties ofother iron castings, and which also substantially con tributes to theprevention of the earthy particles of the mold or core from beingembedded into or-adhering to thesurfaces of the casting. This latterresult is contributed to by the formation of an insulated gas filmbetween the juxtaposed surfaces of the casting and the mold or coreand/or the decomposition in whole or in part upon the surfaces of themold or core of some one or more of the aforesaid ingredients mixed withthe earthy particles forming the main body of the mold or core.

Castings of all kinds, and more especially of molten metal, made in thepractice of my method may be cleaned at a fraction of the cleaning costrequired prior art. To demonstrate the practical utility of my saidmethod, I employ a mold and/or core constructed in accordance with mysaid method and have made and caused to be made many kinds of castingsinsuch molds and/or cores of many different kinds of metals and theiralloys and other cast substances.

Instead of the employment of latex as above described the practice of mymethod may be advantageously accomplished by the employment of latexembodying the particles or a rubber solution that had been vulcanized tothe desired degree or the employ ment of artificial latex and/or rubberor rubber-like dispersions and/or the product or products of latex,rubber, or rubber-like substances in dispersion or otherwise, includinsuch substances or the rubber base thereo as may have been treated byanother substance such, for instance, as a sulphonic acid, a halogen, ora substance which may have modified some of the properties whichordinarily characterize rubber or rubber-like substances. The amount ofthe latex rubber or rubber-like substance or the derivative thereofemployed in the practice of my method depends upon the degree ofstrength required in the mold and/or core required for the eflicientproduction of a casting of given characteristics. For instance, moldsand/or cores having relatively thin areas which are more liable tocrumble or be broken off in normal handling or production, or towashinto the fluid material being cast should have greater strength. Suchgreater strength may be obtained at will by the employment of a greaterpercentage of a more concentrated solution, a variation of theingredients of the mixture, including the possible increment of theamount of accelerant of vulcanization, or the increment of the period orrate of the curing or vulcanization of the mold and/or by the practicesof the core, which those having skill in the art may readily determinefrom the characteristics of the desired casting and/or thecharacteristics of the metal, alloy or substance to be cast. I

In the attainment or molds and or cores of greater strength, where theaforesaid substance or substances employed therefor may in any caseresult in the constituents of the mold or core becoming too moist foradvantageous construction of the mold or core therefrom, which conditionis readily recognizable by those skilled in the art, the excess moisturemay be readily removed therefrom by any of the practices employed in theart, including the prolonged tempering and aeration of the materialand/or its being subjected to normal atmospheric or an elevatedtemperature.

In this specification and its appended claims where the term, hydratedrubber, is. employed it is also intended to include rubber either aslatex, c'oagulated rubber, rubber dis- -persions, artificial latex, ofsap from trees such as H e'vea brazz'lz'ensis, or from vines or shrubs,as well as from other kindred vegetation such as guayule containing moreor less rubber hydrocarbon. The rubber may be unvulcanized or consistofvulcanized soft' rubber, and may have been previously subjected to anelevated temperature.

It may also include any rubber or scrap rubber, either or both, that hasbeen sub-. jected to an elevated temperature alone or in the presence ofsulphuric acid or a} sulphonic acid 'or'a sulphonyl halide or it mayalso include asubstance such as is an article of commerce under the nameThermoprene. Itmay' also include dispersions of one or more of saidsubstances.

In the development of my present invention I havemade or caused to bemade many molds and/or cores for different types of castings ofdiiierent metals, compositions, or materials, and have employed therein,separately and in combinat1on,the various --materials hereinbeforestated, and have attained satisfactory results in substantially allre-'- spects therewith.

In this art, binders for the constituents of cores and molds long havebeen recognized compositions of commerce used in the production of moldsand cores for the mak-. ing of castings of hot metal.

The molds and/ or cores made in accordance with my invention are notrequired, as in the prior art, to be used soon after their productionnor are they required to be handled with the care of such production ofthe prior art, and that the molds and/or cores produced in accordancewith my method posforming a casting at'a remote period after theirproduction.

The material with which the are mixed tends to prevent the absorption ofmoisture by the molds and/or cores and hence does not require the carewith respect to moisture proof stora e nor as to the humidity of theirsurroun ing atmosphere as do molds and/or cores of the prior art. VVhi1ethe ingredients which I employ in mixing with the sand or other bodyportion of the molds and/or cores are higher in cost than the moldand/or core binders of the prior art, yet the percentage of suchmaterials added to the mold and/or core material is relatively smalleven with castings requiring the greatest strength of mold and/or core.The difference in the cost of my binding materials is very much lessthan the saving which their use entails even in the one item of thecleaning cost of the castings. This renders the use of my method andmeans profitable even in'the one item of cast-ing cleaning costs whileits numerous other advantages constitute additional gains and savingsordinarily and usually occurring from the practice of my said method.

In the production of molds and/or cores of relatively large areas afurther saving may be obtained by the construction of the surfaces ofthe mold and/0r core to a desired thickness by'the molding sand mixedwith my said binder and then backing the same up with the molding sandof the prior art.

This invention is in furtherance and continuance of, and an lmprovementupon, the

invention set forth in my pending applicato likewise entitled andbearing Serial No. 332,225.

The invention herein described maybe manufactured and used by or for theGovernment of the United States for governmental purposes without thepayment to me of any royalty thereon or therefor.

Having now so fully described my invention that others skilled in theart may there- 45 from make and use the same, what I claim and desire tosecure by Letters Patent is 1. The method of producing molds or corescomprising selecting the molding sand or components, tempering the samewith a hydrated rubber mixture, making the mold or core by employingsaid tempered components, and dehydrating the mold or core to thedesiredextent.

2. The method of producing molds or cores including the step of applyingto constituents of the mold or core a hydrated rubber mixture.

3. The method of producing molds or cores comprising selecting themolding sand or components, tempering the same with a hydrated rubbermixture containing an added coloid, making the mold or core by employingsaid tcu'ipered components, and dehydrating the mold or core to thedesired extent.

4. The method of producing molds or cores comprising selecting themolding sand or components, tempering the same with a hydrated rubbermixture containing an added colloid to the desired consistency, andmaking the mold or core by employing said tempered components.

5. The method of producing molds or cores including the step of applyinga liquid containing a colloid to constituents of the mold or core, andapplying to constituents thereof a hydrated rubber mixture.

6. As a new article of manufacture, a mold or-core containing a hydratedrubber.

7. As a new article of manufacture, a mold or core containing smallparticles and by drated rubber substantially intimately mixed therein.

8. The method of making castings including the steps of forming a moldor core from material of small particles bound together in whole or insubstantial part by a hydrated rubber material, and forming the castingin contact with said mold or core.

9. The method of making castings including the steps of forming a moldor core from material of small particles bound together in whole or insubstantial part by a hydrated rubber material, dehydrating the saidmold or core material to the desired consistenc and forming the castingincontact with-sald mold or core.

10. A binder forthe constituents of molds or cores in the production ofa mold orcore for the making of castings of molten steel, iron, brass,aluminum and the like high melting point metals, said binder containinghydrated rubber.

11. A binder for the'cons'tituents of'molds or cores in the productionof a mold or core for the making of castings of molten steel, iron,brass, aluminum and the like highmelting point metals, which bindercontains rubher and an added colloid. 1

12. The method of decreasing the surface tension of a core binder in theproduction of a mold or core for the making of castings of molten steel,iron, brass, aluminum and the like high melting point metals, saidbinder including a hydrated rubber solution, consisting of adding acolloid to said hydrated solution.

13. A mold or core formed of refractory particles at least some of whichare bound together by a liquid containing particles of a binder selectedfrom the 'class comprising rubber and rubber derivatives, said liquidalso containing a protective colloid in quantity suflicient to keep saidparticles suspended in said liquid, said bound granules being locatedwithln an area of the mold or core subjected to, and at least some ofthe binder in said area being adapted to be volatilized by, the heat ofthe cast metal in contact with said mold or core. I

14. A mold or core having refractory particles at least some of whichare bound together by a liquid containing particles of a binder selectedfrom the class of rubber and rubber derivatives, and said liquid alsocontaining a colloid selected from the class comprising gelatin, agaragar, glue, sodium and ammonia soaps, and extract of uince seed. CHARLESMARSHALL SAE ER, JR.

